Lexan for jigs

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I have shattered polycarbonate, all it takes is a bad design with sharp inside corners. Avoid that and the stuff is literally bullet proof.
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Roger Shoaf
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Really, lexan (polycarbonate) is very different from plexiglass (acrylic) in how it reacts to stress & strain. Plexiglass will shatter quite easily but lexan usually deforms. You can actually bend the thinner stuff in a sheet metal brake.
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Larry Wasserman Baltimore, Maryland
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Where can one purchase Lexan and what sizes does it come in?
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Any plastics place. It's quite common. 4x8 sheets. Thickest I've seen it was 2".

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CW wrote:

Normally Lexan (polycarbonate) will bend into a pretzel long before it shatters, but there is one way to make it brittle. Lexan is mechanically tough, but chemically it's weak. Lots of common chemicals, including household solvents and detergents, can change its behaviour like this.
I used to work on big production-line machinery. One toolroom had a mis-match between its very expensive 1/2" Lexan safety shields around all the CNC machines and the cutting fluid they were using. Eventually there was a mishap on one machine and a chunk of metal came loose. It hit the screen and went straight through it, shattering the glazing like a Hollywood saloon window. They had to change cutting fluids, then replace every screen in the place.
Normally I'd have scrounged the scrap, but this stuff was so embrittled that plant maintenance couldn't even unbolt the screen panels from the frames without most of them cracking or breaking.
I'd also advise against Lexan for jig making. You don't need that level of impact resistance and the stuff's a pain to work with.
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I would think it would work but after some use it would scratch up badly. I'm unsure of its stability with heat. It melts easily. I use 9mm Baltic Birch (3/8") Plywood. Stable and strong.
Dave
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upand_at snipped-for-privacy@yahoo.com wrote in

Lexans attribute is that it does not scratch as easily as other plastics. I use 3/8 all the time for jigs. It is used as trays and stuff for wheelchairs. 1/4 is a little thin for a sled but I think it will work if you are careful. Chamfer edges, holes and slots; cracks will propagate.
Bill
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Actually Lexan (Polycarbonate) is much softer than acrylics like Plexiglass. That is what gives it its impact resistancs, down side is at does scratch much easier than Plexiglass.
Also cost about 2X Acrylic, 1/4" thk is around $10.00 sq/ft.
Kevin
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1/4" will probably flex too much for a sled
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upand_at snipped-for-privacy@yahoo.com wrote:

I usually have piles of plywood and MDF cabinet offcuts available for jigs. I would have to purchase Lexan to use it. Wood is easier to shape, brad nail, and glue for a quick jig. Typically, I'll buy Lexan, UMHW, plastic laminate, metals... only when I have a specific requirement, and only if it'll be for a many-use tool.
Look in any metal shop,, wood shop, plastics shop, etc... Most shop jigs will be made from whatever materials they often work with, because they have some, they work with the material often, and the correct tools and sundries are already handy.
The bottom line is if you like to spend time and effort building pretty jigs, Lexan would probably work fine. Aluminum is nice, as well. On the other hand, if you make many jigs on the spot, specifically for an operation at hand... There's nothing wrong with either approach, it's a personal choice.
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Ahhh yes... the acrylic/Lexan mistaken identity. A simple flame test tells the difference. Google it, because my lawyer advises against sayng too much *G*
Lexan is good enough for jet-fighter canopies, I'm told.
But the whole discussion is moot because all you need to do is call for a price on Lexan.
I have built many a display case for a variety of jewelry stores, and often used Lexan with a sheet of glass on top (scratch restance and hammer resistance in an affordable sandwich).
In my solid surface fabrication, I make a lot of jigs/patterns/templates, and I invariably use MDF and Baltic Birch...OR..solid surface left-overs.
My favourite jig material is 1/2" phenolic, which can be bought with laminate already attached.
Nothing quite like it.
r
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Lexan is good stuff. The down side is that 1/4 inch is really flexible so you would have to back it up with the plywood anyway. Cost is also an issue unless you have it scrap.
Others have mentioned shattering. If you avoid sharp inside corners impact resistance goes through the roof.
Poly carbonate is rather soft and will scratch easily. They do make a scratch resistant grade but it is usually used for glazing.
One thing that does work great for jigs is Formica laminated wood/MDF/particle board. The particle board is the last choice except for cost if you can get sink cutouts cheap and or free. Good till you drop it or get it wet.
--

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Roger Shoaf

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upand_at snipped-for-privacy@yahoo.com wrote:

the best thing I've found, just from working with my own shop scrap is 1/4" melamine coated MDF.
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